This invention relates to an apparatus for profiling, truing or dressing with precision a millstone which is agglomerated with abrasives, by cutting using separate diamond profiling tools. This apparatus may be mounted on the grinding head or possibly on the work table of a grinder, whatever the grinding functions of the latter.
In particular, this invention relates to an apparatus which makes it possible to true an abrasive millstone precisely and rapidly, along difficult and precise contours, the purpose of this millstone being to ensure a perfect finishing work by grinding parts which are machined by means of a planer, a shaper, a mortising machine, a milling machine or a lathe, while correcting an allowance which is provided during machining in order to counter-balance any possible deformations which would entail a subsequent thermal or chemical treatment of the part which has been machined, for example a tempering or cementing treatment of said part.
Apparatuses are known for profiling an abrasive millstone by means of profiling diamonds supported by two separate truing arms of a two-position turret, one of the diamonds being to rough-shape the profile of the millstone, and the other to finish this profile. These known apparatuses may be mounted on a spindle frame of a grinder.
The use of pivoting truing arms makes it possible to correctly select the diamond cutting tool which is suitable for each operation, for example for the rough-shaping of the millstone profile, while leaving an adequate allowance to absorb the surface irregularities caused by the chattering of the millstone. This division of the truing of the millstone into two stages makes it possible to reduce the truing time and to prolong the life of the diamond cutting tools.
However, a major disadvantage of pivoting truing arms is that they have a considerable overhang. This overhang presents quite a substantial obstacle to ensuring a positioning, without clearance, and a precise guidance of each of the diamond tools.
Moreover, these pivoting arms require the presence of a turret slide which is either to slide directly on the bench, or on an intermediate bed plate. In some recent machine tools, such as described in U.S. Pat. No. 2,587,172, the various positions of the turret are not determined by longitudinal and transverse stops, but by microswitches which are connected to a relay system, making it possible to fix all the sources and the sequence of operations.
The advance and translation mechanisms of the truing arms carried by the turret which is mounted on the turret slide are controlled by hydraulic means and are activated in response to a profiling and truing command which is transmitted by a feeler needle passing through a gauge, and by a pantograph system. The transmission ratio is generally one tenth or one fifth with respect to the gauge. Measuring instruments which are formed, for example from a control balance and a comparator make it possible for the diamonds to be adjusted with respect to the axis of rotation of the abrasive millstone.
However, these known profiling apparatuses which have a gauge do not allow the production of profiles having sharp edges.
These known apparatuses suffer from a second disadvantage. They have only two truing tools which are oriented in the same direction. This drawback is also found in dressing apparatus when an abrasive millstone is dressed with cubic boron nitride. The binder must be removed under carefully controlled conditions to avoid a premature baring of the hard abrasive grains. The absense of tools having different orientations simultaneously impairs the precision of machining and the life of the millstone.